1. Field of the Invention
This invention relates to a camera capable of flash photography, and in particular to a camera improved so as to emit light simultaneously with the start of movement of the rearward shutter curtain of a focal plane shutter.
2. Related Background Art
In a camera with a focal plane shutter, there has heretofore been proposed the so-called rearward shutter curtain synchronization in which an electronic flash device is caused to emit light immediately before the rearward shutter curtain begins to be closed, that is, immediately before the rearward shutter curtain starts to be moved. In such prior-art camera, a rearward shutter curtain switch provided to output a trigger signal for starting the wind-up of the motor drive, i.e., a switch adapted to be closed with the start of movement of the rearward shutter curtain, is used also as a switch for producing a trigger signal for rearward shutter curtain synchronization.
However, this rearward shutter curtain switch is a mechanical contact and therefore has suffered from a disadvantage that there is certainly a delay time after the start of movement of the rearward shutter curtain and before the curtain is closed.
This will hereinafter be described with reference to FIG. 5 of the accompanying drawings. FIG. 5(a) indicates the locuses of the forward and rearward shutter curtains relative to the film picture plane by FC and RC, respectively. In this figure, A indicates the position in which the end of the shutter curtain appears in the exposed area of the film, and B indicates the position in which the end of the shutter curtain leaves the exposed area of the film. From FIG. 5(a), it is clear that both the forward and rearward shutter curtains have auxiliary movement during times t.sub.1 and t.sub.2 from after the start of movement thereof until the shutter curtain appears in the picture plane. Referring to FIGS. 5(d) and 5(e), the aforementioned rearward shutter curtain switch which is a mechanical contact is certainly closed in a delay time t.sub.3 after the start of movement of the rearward shutter curtain, and on the basis of this ON signal, the light emission of the electronic flash device is obtained at a timing indicated by FR1.
In recent years, however, higher speeds of shutters have been contrived and the auxiliary movement time t.sub.2 tends to be very much shortened, and depending on the delay time t.sub.3, the rearward shutter curtain appears in the picture plane before the flashing of the electronic flash device is not terminated and thus, eclipse or irregularity of exposure occurs. Also, the light emission of the electronic flash device depends on the mechanical contact, and this has led to inferior reliability.
Heretofore, as shown in FIGS. 5(b) and 5(c), in the case of forward shutter curtain synchronization, the light emission of the electronic flash device has been obtained at a timing indicated at FF by an x contact being closed simultaneously with the termination of movement of the forward shutter curtain.